79 Swingarm

[Hoko]

Can I use a larger rear tire if I put a 79 swingarm on my 78?

[Re-run]

How big were you thinking? I know a 140 will fit the 78 swingarm, maybe even a 150. I don't think the 79 arm will allow anything bigger than that.

[Hoko]

Re-run wrote

How big were you thinking? I know a 140 will fit the 78 swingarm, maybe even a 150. I don't think the 79 arm will allow anything bigger than that.

I haven't considered an exact size yet.  One guy had his swingarm cut and welded to accomodate a large rear tire and he said it has really increased handling stability.  I also noticed all the gp bikes that race here at Circuit of the Americas have huge rear tires.

[shinyribs]

My '80F had a 170 on the back in an un-cut swingarm. Front sprocket had to be stepped out, tho.

[rvandope]

I imagine your limitation will be your rear brake linkages, not your actual swingarm. May have to modify them to clear the rim/tire. I'm looking into doing the same right now. I've heard a 150 is possible on the '79 swingarm.
Reaslistically though, you will sacrifice turn-in responsiveness and wont be as nimble. I'm looking to upgrade the tire width solely for looks though.

[Re-run]

The other issues are increased tire wear and less traction. If you put a tire that size on the stock rim, it creates a pinch on the tire. The profile is no longer as designed. This leads to increased wear on the tire and less traction.
The proper way to do this would be to lace a wider rim to the hub. Or get a wider wheel if you have comstars.